Question: $11 \times 20.9 = $
Explanation: ${1}$ ${1}$ ${2}$ ${0}$ ${9}$ ${\times\vphantom{0}}$ ${.}$ ${1}\times {0.9}= {0.9}$ ${9}$ ${10}\times {0.9}= {9}$ ${9}$ ${1}\times {0}= {0}$ ${0}$ ${0}$ ${10}\times {0}= {0}$ ${0}$ ${1}\times {20}= {20}$ ${2}$ ${0}$ ${0}$ ${10}\times {20}= {200}$ ${2}$ ${+\vphantom{0}}$ ${2}$ ${2}$ ${9}$ ${9}$ ${+\vphantom{0}}$ ${2}$ ${2}$ ${9}$ ${9}$ ${.}$ The top number has $0$ digits to the right of the decimal. The bottom number has $1$ digit to the right of the decimal. The product has $0+1=1$ digit to the right of the decimal. $11 \times 20.9 = 229.9$